1. Field of the Invention
This invention relates to thermally insulating materials, and more particularly to inorganic cellular materials.
2. Description of the Prior Art
A wide variety of both inorganic and organic materials have been employed for thermal insulation of building structures.
For example, inorganic materials such as fiberglass and so called rock-wood find widespread application in the United States for residential housing.
More recently, organic materials such as polyurethane foam, and styrofoam have been used primarily for other than residential housing applications.
While the prior art materials exhibit varying degrees of effectiveness as thermal insulators, none of the prior art materials has been completely satisfactory from an overall standpoint.
For example, while the organic foams, in general have better thermal insulative properties than fiberglass, the fire retardant and smoke emission characteristics of the organic foams are less than optimum. Indeed, even fiberglass insulation is found to emit large quantities of smoke when exposed to the flame of a propane torch.
Prior art materials also exhibit varying degrees of shrinkage, ranging from approximately 8% to 25%, which shrinkage reduces their effectiveness as a thermal insulator.
Also, the prior art materials are relatively expensive and require raw materials and processing not readily available in many areas of the world. Since the world in general has a shortage of residential housing, this is a decided disadvantage.